structure, classification and functions of amino acids

detailed notes on amino acids and proteins

1. © 2010 Pearson Education, Inc.
Chapter 6: Proteins and
Amino Acids

2. © 2010 Pearson Education, Inc.
What Are Proteins?
Large molecules
Made up of chains of amino acids
Are found in every cell in the body
Are involved in most of the body’s functions and life
processes
The sequence of amino acids is determined by DNA

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Structure of Proteins
Made up of chains of amino acids; classified by number of
amino acids in a chain
•Peptides: fewer than 50 amino acids
-Dipeptides: 2 amino acids
-Tripeptides: 3 amino acids
-Polypeptides: more than 10 amino acids
•Proteins: more than 50 amino acids
-Typically 100 to 10,000 amino acids linked together
Chains are synthesizes based on specific bodily DNA
Amino acids are composed of carbon, hydrogen, oxygen,
and nitrogen

4. Structural Differences Between Carbohydrates,
Lipids, and Proteins
Figure 6.1

5. The Anatomy of an Amino Acid
Figure 6.2b

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Peptide Bonds Link Amino Acids
Form when the acid group (COOH) of one amino acid joins
with the amine group (NH
2) of a second amino acid
Formed through condensation
Broken through hydrolysis

7. Condensation and Hydrolytic Reactions
Figure 6.3

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Essential, Nonessential, and Conditional
Essential – must be consumed in the diet
Nonessential – can be synthesized in the body
Conditionally essential – cannot be synthesized due to
illness or lack of necessary precursors
•Premature infants lack sufficient enzymes needed to
create arginine

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Structure of the Protein
Four levels of structure
•Primary structure
•Secondary structure
•Tertiary structure
•Quaternary structure
Any alteration in the structure or sequencing changes
the shape and function of the protein

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Denaturing
Alteration of the protein’s shape and thus functions through
the use of
•Heat
•Acids
•Bases
•Salts
•Mechanical agitation
Primary structure is unchanged by denaturing

12. Denaturing a Protein
Figure 6.5

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Quick Review
Proteins are chains of combination of amino acids
Amino acids contain carbon, hydrogen, oxygen, nitrogen,
and sometimes sulfur
Unique amino acids consist of a central carbon with a
carboxyl group, a hydrogen, a nitrogen-containing amine
group, and a unique side chain
There are 20 side chains and 20 unique amino acids
•9 essential amino acids
•11 nonessential amino acids
-At time these become conditionally essential
Amino acids link together with peptide bonds by
condensation and break apart by hydrolysis

14. © 2010 Pearson Education, Inc.
Quick Review
Attractions and interactions between the side chains cause
the proteins to fold into precise three-dimensional shapes
Protein shape determines its function
Proteins are denatured and their shapes changed by
•Heat
•Acids
•Bases
•Salts
•Mechanical agitation